This article explains the key differences between orthographic and perspective projection, highlighting how orthographic projection preserves the true dimensions of objects without distortion, while perspective projection introduces perspective distortion as objects move further from the Center of Projection. It emphasizes the importance of orthographic projection in fields like technical drawing, architecture, and CAD, where accurate representation of object dimensions is essential.
Alexander S. Ricciardi
September 15th, 2024
Orthographic projection is a type of parallel projection. Parallel projection is a projection where rays (or projectors are parallel whereas in Perspective projection, the rays converge towards a single point (the camera or eye). Meanwhile, Orthographic projection is when objects are projected perpendicularly onto the viewing plane, maintaining their dimensions. Multiple differences exist between the two projections see Table 1; however, the key difference between Orthographic and Perspective projections is that in Orthographic projection, the size and shape of objects remain consistent on the projection plane without perspective distortion (Adware, 2020). Perspective distortion occurs in a Perspective projection as an object gets further away from the Center of Projection (COP) distortion the shape of the object. Figure 1 illustrates the two projections.
Figure 1
COP vs DOP
Note: The Center of Projection (COP) represents a Perspective Projection, and the Direction of Projection (DOP) represents the Parallel Projection. From Chapter 5: Viewing. Interactive computer graphics. 8th edition, p134, by Angel and Shreiner (2020).
Table 1
Difference Between Parallel Projection and Perspective Projection
Note: From “Difference between Parallel and Perspective Projection in Computer Graphics” by Aware (2020).
As listed in the table above Orthographic projection is one of the two types of Parallel projection, and it is used to represent 3D objects in two dimensions by projecting them orthogonally onto a viewing plane. It is commonly used in drawings, architectural designs, and Computer-Aided Design (CAD) for 3D modeling, where preserving the true dimensions of objects without introducing perspective distortion is crucial.
By preserving the size of the object without distortion, orthographic projection offers clear advantages for the fields listed above.In drawings, it allows for the accurate representation of objects’ dimensions, bringing clarity and a better understanding of the object's shape, which is essential for technical drawings.In architectural design, Orthographic projection preserves the true dimensions of building elements such as walls, windows, and doors, ensuring that these dimensions are accurately communicated to builders and that the final construction reflects the architect(s)'s intent.
In Computer-Aided Design (CAD) for 3D modeling, Orthographic projection prevents perspective distortion of the object dimensions allowing 3D prevents perspective distortion, allowing 3D models to retain the objects' true dimensions when scaled up or down, making the models easily transferable for use in simulations and manufacturing.
To summarize, Orthographic projection is a type of Parallel projection, where an object is projected orthogonally onto a viewing plane. The key difference between Orthographic projection and Perspective projection is that Orthographic projection preserves the size and shape of objects without distortion, while perspective projection does not. Orthographic projection is essential for fields such as drawings, architectural designs, and CAD for 3D modeling, where preserving the true dimensions of objects without introducing distortions is crucial.
References:
Adware (2020, May 24). Difference between parallel and perspective projection in computer graphics.
GeeksforGeeks. https://www.geeksforgeeks.org/difference-between-parallel-and-perspective-projection-in-computer-graphics/
Angel, E., & Shreiner, D. (2020). Chapter 5: Viewing. Interactive computer graphics. 8th edition. Pearson Education, Inc. ISBN: 9780135258262
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